By way of background, lossy image compression techniques, such as JPEG, Wavelets and Vector Quantization, typically provide high compression ratios and good image quality for pictorials, whereas lossless techniques, such as JPEG-LS, run-length encoding, and various Lempel-Ziv approaches, typically produce good compression results on images containing line art or graphics. Whenever both pictorials and graphics appear on the same image, the exclusive use of a lossy technique often produces unsatisfactory image quality, whereas the exclusive use of a lossless approach often produces unsatisfactory compression ratios. It is to be appreciated that the aforementioned compression techniques, as well as many others, are well known to those of skill in the art and require no detailed description herein.
In addition, a system is desired that requires no apriori knowledge of the imagery content of a specific region or regions of an image. Furthermore, a system is desired for printing applications, where excellent image quality is required along with compression ratios that are high enough to be compatible with the storage and data bandwidth requirements of the printers being used.
The present invention contemplates a new and improved method and apparatus for controlling image quality and compression ratios that resolve the above-referenced difficulties and others.